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101.
Suresh K. Sahni Israel Cabasso 《Journal of polymer science. Part A, Polymer chemistry》1988,26(12):3251-3268
Glycerol, D -mannitol, and D -sorbitol were converted into their mono- and di-O-1,3-dioxolane and 1,3-dioxane bromoethylidene derivatives through a transacetalation reaction with bormoacetaldehyde diethyl acetal under controlled conditions. These brominated dioxolane or dioxane derivatives were subsequently phosphonylated through the Arbuzov reaction. The phosphonylated cyclic acetals were used as precursors for the synthesis of acrylated phosphonate monomers. All these compounds have been characterized by elemental analysis and spectroscopic (IR, 1H-,13C-, 31P-NMR and mass) methods. A mixture of 1,3-dioxane and 1,3-dioxolane derivatives was obtained with D -sorbitol, whereas the reaction products with glycerol and D -mannitol yielded primarily the 1,3-dioxolane derivatives. The acrylated phosphonates of glycerol and mannitol have been polymerized and studied on the basis of gel permeation chromatography and their spectral and thermal properties. The acrylated phosphonates, monomers, and polymers, were shown to have a large capacity to solvate and dissolve heavy metal salts. This results in a dramatic increase (> 100°C) of the glass transition temperature of these polymers. 相似文献
102.
Varun Sahni 《Pramana》2000,55(1-2):43-52
I present a short overview of current observational results and theoretical models for a cosmological constant. The main motivation
for invoking a small cosmological constant (or A-term) at the present epoch has to do with observations of high redshift Type
Ia supernovae which suggest an accelerating universe. A flat accelerating universe is strongly favoured by combining supernovae
observations with observations of CMB anisotropies on degree scales which give the ‘best-fit’ values ΘA ⋍ 0.7 and Θ
m
⋍ 0.3. A time dependent cosmological A-term can be generated by scalar field models with exponential and power law potentials.
Some of these models can alleviate the ‘fine tuning’ problem which faces the cosmological constant. 相似文献
103.
104.
Jasmeet Kaur Md. Khalid Anwer Ali Sartaj Bibhu Prasad Panda Abuzer Ali Ameeduzzafar Zafar Vinay Kumar Sadaf Jamal Gilani Chandra Kala Mohamad Taleuzzaman 《Molecules (Basel, Switzerland)》2022,27(4)
The objective of the current research is to develop ZnO-Manjistha extract (ZnO-MJE) nanoparticles (NPs) and to investigate their transdermal delivery as well as antimicrobial and antioxidant activity. The optimized formulation was further evaluated based on different parameters. The ZnO-MJE-NPs were prepared by mixing 10 mM ZnSO4·7H2O and 0.8% w/v NaOH in distilled water. To the above, a solution of 10 mL MJE (10 mg) in 50 mL of zinc sulfate was added. Box–Behnken design (Design-Expert software 12.0.1.0) was used for the optimization of ZnO-MJE-NP formulations. The ZnO-MJE-NPs were evaluated for their physicochemical characterization, in vitro release activity, ex vivo permeation across rat skin, antimicrobial activity using sterilized agar media, and antioxidant activity by the DPPH free radical method. The optimized ZnO-MJE-NP formulation (F13) showed a particle size of 257.1 ± 0.76 nm, PDI value of 0.289 ± 0.003, and entrapment efficiency of 79 ± 0.33%. Drug release kinetic models showed that the formulation followed the Korsmeyer–Peppas model with a drug release of 34.50 ± 2.56 at pH 7.4 in 24 h. In ex vivo studies ZnO-MJE-NPs-opt permeation was 63.26%. The antibacterial activity was found to be enhanced in ZnO-MJE-NPs-opt and antioxidant activity was found to be highest (93.14 ± 4.05%) at 100 µg/mL concentrations. The ZnO-MJE-NPs-opt formulation showed prolonged release of the MJE and intensified permeation. Moreover, the formulation was found to show significantly (p < 0.05) better antimicrobial and antioxidant activity as compared to conventional suspension formulations. 相似文献
105.
106.
Tariq Mohammad Iqbal Zeenat Ali Javed Baboota Sanjula Parveen Rabea Mirza Mohd. Aamir Ahmad Sayeed Sahni Jasjeet Kaur 《平面色谱法杂志一现代薄层色谱法》2014,27(2):124-131
JPC – Journal of Planar Chromatography – Modern TLC - A simple, sensitive, precise, rapid, and reliable high-performance thin-layer chromatographic (HPTLC) method for the simultaneous... 相似文献
107.
The Effect of Wettability on Three-Phase Relative Permeability 总被引:3,自引:0,他引:3
We study three-phase flow in water-wet, oil-wet, and fractionally-wet sandpacks. We use CT scanning to measure directly the oil and water relative permeabilites for three-phase gravity drainage. In an analogue experiment, we measure pressure gradients in the gas phase to determine the gas relative permeability. Thus we find all three relative permeabilities as a function of saturation. We find that the gas relative permeability is approximately half as much in a oil-wet medium than in an water-wet medium at the same gas saturation. The water relative permeability in the water-wet medium and the oil relative permeability in the oil-wet medium are similar. In the water-wet medium the oil relative permeability scales as k
roS
o
4 for S
o>S
or, where S
or is the waterflood residual oil saturation. With octane as the oil phase, k
roS
o
2 for S
o<S
or, while with decane as the oil phase, k
ro falls sharply for S
o<S
or. The water relative permeability in the oil-wet medium resembles the oil relative permeability in the water-wet medium for a non-spreading oil such as decane. These observations can be explained in terms of wetting, spreading, and the pore scale configurations of fluid. 相似文献
108.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
109.
The layered manganite Nd2−2x
Sr1+2x
Mn2O7, with x varying between 0 and 0.5, has been synthesized using solid-state reaction method. We have found that Nd2−2x
Sr1+2x
Mn2O7 do not form the single-phase layered compound with A3B2O7 structure. Instead, mixtures of various phases, such as, orthorhombic perovskite, i.e., Nd1−z
Sr
z
MnO3, layered manganite and unreacted starting compounds, have been obtained. Except for x=0.4, which is found to be an antiferromagnetic insulator, all other x values yielded metal-insulator transition and ferromagnetic ordering. 相似文献
110.
I. Quasim A. Firdous N. Sahni S. K. Khosa P. N. Kotru 《Crystal Research and Technology》2009,44(5):539-547
Growth of pure‐, sodium‐ and lithium‐ doped potassium hydrogen tartrate single crystals by gel technique is reported. Growth conditions conducive for the growth of single crystals are worked out. The crystals are characterized by using powder XRD, SEM, FTIR, AES, EDAX, CH analysis and thermoanalytical techniques. The stoichiometric composition for the grown crystals are established as KHC4H4O6.H2O, (K)0.98(Na)0.02.H2O and (K)0.94(Li)0.06HC4H4O6.H2O. Doping of sodium and lithium in the pure potassium hydrogen tartrate single crystals is found to influence the size, perfection, morphology, crystal structure and the thermal stability of crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献